In recent years, development of time-of-flight range image sensors using semiconductors is actively being carried out. For example, a range image sensor includes a plurality of lock-in pixels arrayed and connected in parallel for transferring carriers generated in photodiodes in synchronization with a light source to a plurality of charge accumulators, while each lock-in pixel element is made into a smaller pixel so as to transfer charges at high speed as disclosed in Patent Literature (PTL) 1.
In the image sensor disclosed in PTL 1, load capacitances of a plurality of transfer gates connected in parallel increase, and the entire power consumption increases as the number of pixels increases. Further, connecting a plurality of lock-in pixel elements increases the area of a diffusion layer of a signal detector, which may cause a dark current.